<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        {{ item.name }}
        <button @click="add(index)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr v-for="(item, index) in arr" :key="item.name">
        <th>{{ index + 1 }}</th>
        <th>{{ item.name }}</th>
        <th>{{ item.price }}</th>
        <th>{{ item.count }}</th>
        <th>{{ item.price * item.count }}</th>
      </tr>
    </table>
    <p>总价格为:{{ all }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods: {
    add(n) {
      this.arr[n].count += 1;
      // this.m = this.num * this.arr[n].price;
    },
  },
  computed: {
    all() {
      return this.arr.reduce((sum, obj) => {
        return (sum += obj.price * obj.count);
      }, 0);
    },
  },
};
</script>
